1. Field of the Invention
This invention relates generally to methods and apparatus for installing and suspending coiled tubing in an oil and/or gas well, and more particularly to a method and apparatus for installing and suspending coiled tubing utilizing a tubing hanger with a hydraulically actuated slip and sealing assembly.
2. Description of the Prior Art
Coiled tubing has gained widespread acceptance in the last decade due to its many advantages over conventional jointed tubing, including time and labor savings, pumping flexibility, elimination of leakage and leak testing, reduced formation damage, safety, etc. The operational concept of a coiled tubing system involves running a continuous string of smaller coiled tubing into a well to perform specific well servicing operations without disturbing existing completion tubulars and equipment. When servicing is complete, the small diameter tubing may be retrieved from the well and spooled onto a large reel for transport to and from work locations.
The typical procedure for hanging or suspending coiled tubing from the surface as a production or an injection string utilizes a tubing head installed above the lower master valve in which an annular tubing hanger with slips and seals is supported and blowout preventers connected above the tubing head. The typical wellhead assembly also includes an access window assembly disposed above the blowout preventers and requires that the distance from the bottom flange of the access window assembly to the tubing head lockdown screws be measured to insure that the annular hanger assembly sets completely in its hanger profile. In wraparound style hanger assemblies the hanger (with slips and seals) is placed around the coiled tubing and slowly lowered to the top of the lower set of blowout preventers rams. The hanger assembly is lowered into the hanger bowl of the tubing head and the weight of the tubing is landed on the hanger. Lockdown screws are then engaged to actuate the seal of the hanger, and the coiled tubing is rough cut through the window of the access window assembly and the blowout preventers and access window assembly are removed. A final or smooth cut is then made on the coiled tubing and it is beveled to fit an adapter and to avoid damaging adapter seals. The remaining wellhead equipment is then installed and flow lines connected. The coiled tubing is pressured up to shear out the bottom plug and the well is placed in service.
In installations having an access window assembly, it is necessary to open the access window assembly for placement of the slip and seal assembly around the coiled tubing so that it may be lowered into the tubing head, which potentially opens the annular space surrounding the coiled tubing to the pressure in the well. Also, the fact that the hanger assembly must be lowered around the coiled tubing from a point near the bottom of the access window assembly to the seating area in the tubing head, without being seen, provides a potential for improper seating of the hanger seal and actuation of its slips. Furthermore, the wrap-around slip and sealing assemblies of the hangers are inherently more likely to create sealing or slip engagement problems than seal or slip assemblies that are continuous.
There are several types of tubing hanger assemblies for suspending coiled tubing that utilize mechanical means for actuating slips or clamping jaws to hold the tubing rigidly at a predetermined position in the annulus of a wellbore. These types of hanger assemblies typically include semi-circular gripping and support members which are clamped about the tubing at a designated position and maintained clamped with a circular array of threaded rods or set screws that maintain clamping pressure to retain the tubing, and are accessible from outside of the hanger assembly. In many of these tubing hanger assemblies, the threaded rods, actuator rods, or set screws, when rotated, move the slips downward and inward to a position adjacent the tubing in gripping relationship and simultaneously, as the slips move downward and inward, they bear against a slip support cup adjacent the central bore which, in turn, compresses a packer element to expand inward into contact with the tubing thereby to seal off the annulus immediately around the coiled tubing.
Cobb, U.S. Pat. Nos. 4,554,971 and 4,646,827 discloses a tubing anchor assembly for seating and supporting coiled tubing in a tubing head, which includes as a first element, a slip assembly characterized by multiple slip segments inserted in the slip bowl of the tubing head and each provided with a beveled top face and a vertically oriented dove tail slot. As a second element, slip retainer screws are radially threaded in the tubing head body at spaced intervals, each of the slip retainer screws provided with a frustro conical tip having a beveled tip base, and each tip extending into the slip bowl of the tubing head and engaging a dove tail slot in one of the slip segments. The slip segments are maintained in open configuration inside the upper portion of the slip bowl when the tips of the slip retainer screws are in engagement with the dove tail slots and when the slip retainer screws are threadedly retracted in the tubing head body. A retainer ring located in a groove provided in each of the slip segments serves to maintain the slip segments in a desired alignment as a slip assembly inside the slip bowl and the slip segments are permitted to drop in concert by the influence of gravity from the frustro conical tips of the slip retainer screws as the slip retainer screws are caused to threadedly travel toward the center of the slip bowl. The slip segments are secured in functional position in the slip bowl after release by engagement of the frustro conical tips with the beveled top faces of the slip segments.
Boychuk, U.S. Pat. Nos. 5,515,925 and 5,515,926 disclose an apparatus and method for suspending coiled tubing in a well which utilizes a tubing head having a vertical flow passage therethrough, an annular sealing assembly carried in a lower counterbored portion of the flow passage, and a slip assembly carried in an upper counterbored portion of the flow passage, and a plurality of circumferentially spaced threaded slip activators carried by the tubing head and connected with the slip assembly. The slip activators are manipulated externally of the tubing head to move the slip assembly from passive positions to active positions. The activators move the slip assembly between an outwardly expanded passive position in which the slip assembly does not interfere with the flow passage and an inwardly contracted active position in which gripping surfaces carried on the slip assembly engages the coiled tubing to support the weight thereof, and the weight of the tubing is transferred from the slip assembly to the sealing assembly.
Piper, U.S. Pat. No. 5,522,464 discloses a hanger assembly for use with coiled tubing, which provides separate hydraulic actuation of slip positioning and setting of a dual packer element. The hanger assembly includes a body member having an axial bore that intersects at an intermediate position with a frusto conical slip bowl wherein a spaced array of upwardly toothed slips is slidably positioned. Plural hydraulic actuators are mounted in the body member and have actuator rods pivotally connected to respective slips to be driven downward and inward into contact with the tubing at a designated position. The lower part of the body member includes a central, cylindrical cavity which receives inner and outer packers in a concentric array with the inner packer defining the central bore such that application of hydraulic fluid under pressure expands the packer inward into sealing relationship around the tubing passing therethrough.
Baker et al, U.S. Pat. No. 5,727,631 discloses a coiled tubing hanger including a hanger bowl, a slip bowl supported in the hanger body, a plurality of slip segments disposed in the slip bowl so as to be movable between a retracted position wherein the tubular member is able to pass through the coiled tubing hanger and an extended position wherein a serrated surface of the slip segments engages the coiled tubing and forces the slip segments along the slip bowl so as to wedge the slip segments between the slip bowl and the coiled tubing to hold the coiled tubing. The slip segments are biased in the retracted position with a pair of slip retaining rings and the slip segments are moved between the retracted portion and the extended position with a plurality of spring-loaded pins disposed through the hanger body and engagable against the outer side of the slip segments such that the slip segments are disposed in the extended position when the pins are urged inwardly and such that the slip segments are biased in the retracted position when the pins are urged outwardly.
Card et al, U.S. Pat. No. 6,588,510 discloses a coil tubing hanger system and method of installation utilizing a tubing hanger body having an axial opening therethrough. A slip bowl having a base and housing a slip that can be retained in a first position spaced apart from bowl base and a second position proximate the bowl base is fitted within the opening. Tubing is fitted within the slip and through the bowl while the slip is retained in the first position. The slip is then allowed to drop to the second position such that the slip teeth bite onto the outer surface of the tubing.
The present invention is distinguished over the prior art in general, and these patents in particular by a tubing hanger apparatus and method for installing coiled tubing in an oil and/or gas well which utilizes a tubing head assembly having a vertical flow passage therethrough, a hydraulically operated activation piston carried in an upper portion of the flow passage, a double tapered slip cup and an annular packoff sealing assembly carried in a lower portion of the flow passage, and a contractible double tapered slip assembly disposed between the piston and the slip cup. The piston is in a normally raised position and the slip assembly is normally radially expanded to allow and coiled tubing to be lowered or raised therethrough and through the slip cup and packoff sealing assembly. The piston is lowered by hydraulic pressure to apply a vertical force and radially contract the slip assembly to grip the tubing and support the weight thereof and the weight of the tubing is transferred through the slip cup to the packoff sealing assembly which expands inwardly to seal the tubing exterior.
In the installation method, the coiled tubing hanger assembly, which includes the tubing head and components described above, is installed on the wellhead prior to lowering the coiled tubing into the well. A blowout preventer stack and coiled tubing injector apparatus is installed above the tubing hanger apparatus. The coiled tubing is run through the blowout preventer stack and coiled tubing head until the string of coiled tubing reaches a desired depth in the well. The activation piston is subjected to hydraulic fluid pressure, such as via a hand pump, sufficient to engage and contract the slip assembly radially inwardly to engage and grip the exterior of the coiled tubing. The coiled tubing is lowered such that the weight of the tubing string is totally supported by the slip assembly, and the slip assembly is engaged with the annular packoff sealing assembly such that the weight of the tubing is transferred through the slip cup to the packoff sealing assembly which expands inwardly to form a sealing relation on exterior of the coiled tubing.
Once all the weight has been set on the slip assembly, the hydraulic pressure is increased sufficient to set and maintain the slip assembly and packoff sealing ring engaged on the tubing. The blowout preventer stack is disconnected from the tubing hanger assembly and lifted with the coiled tubing injector head, and the tubing is cut off above the tubing hanger assembly. A positive lock mandrel/reentry guide threadedly engaged in the top of the tubing head is screwed down to engage the piston and lock the piston and slip assembly in their engaged position on the tubing. The rest of the wellhead is then connected on top of the tubing hanger assembly, and the hydraulic pressure is bled off. To pull the coiled tubing string, hydraulic pressure is applied, and the positive lock mandrel/reentry guide is removed. When the coiled tubing has been re-established to the pulling coiled tubing string and a pressure test has been carried out, then the pressure is bled off to release the slips and packoff seal.
In the present invention, the slips are held in the open position via a set of expansion rings that can be collapsed when hydraulic pressure has been applied via the hydraulically activated piston and have a “controlled makeup” to control the amount of pressure applied to the tubing so they will not crush the coiled tubing, which would otherwise “neck the tubing down” and weaken it at the suspension point.
The apparatus and method of the present invention allows the use of coiled tubing for production applications without requiring removal of the tubing injector apparatus or blowout preventers and without requiring the use of an access window assembly. The present apparatus and method also provides complete pressure control of the well at all times. The slip and seal assemblies are contained within the coiled tubing head but are activated by an external source of hydraulic pressure, and may be easily expanded and contracted to allow the coiled tubing to be repositioned, lower or higher in the well, without pulling the tubing.